The IEEE 1394 high-speed serial bus provides enhanced PC connectivity for consumer electronics audio/video (A/V) appliances, storage peripherals, other PCs, and portable devices, making it possible to transfer content quickly and efficiently around such devices. An industry developed standard, DTCP (5C) copy protection scheme (Digital Transmission Content Protection Specification, Vol. 1, available at www.dtcp.com/info_dtcp_v1.pdf), provides content protection against the unauthorized copying and transmission of digital images and sound. DTCP was developed to encrypt digital content as it moves over an IEEE 1394 interface from pay television systems like cable and satellite. The DTCP scheme supports capabilities such as moving copies from personal video recorders to removable digital tape or disc recordings, and transferring copies among servers located in different places in a home. DTCP technology includes three basic copy control states, designated Copy Freely, Copy One Generation, and Copy Never, any of which can be applied to particular items of content. The DTCP system thus enables generations of control information, where the copy control state of data in a particular location directly affects the next generation copy control state, dependant on the particular copy control in use for the first generation.
In general, pay television systems, as well as MPEG (ISO/IEC JTC1/SC29/WG11)/DVD have been designed to protect content, while controlling the transport stream and delivering clear uncompressed content for display. (DVD specifications are available on the Internet at ecma.ch. Specific specifications include ECMA-267 (97) 120 mm DVD-Read-Only Disk; ECMA-268 (97) 80 mm DVD-Read-Only Disk; and ECMA-272 (99) 120 DVD Rewriteable Disk (DVD-RAM) also published as ISO-IEC 16824).
Digital data is particularly valuable in its clear compressed format, as clear compressed digital data can easily be transmitted because of its size. Additionally, every copy of clear compressed digital data is identical. End to end content protection has shown the importance of maintaining the data encrypted until it is being used; see, for example, the discussion in NDS marketing white paper XTV Persistent End-to-End Content Protection (30 Jul. 2002 publication number XT-M164).
When encrypted video has been decrypted, it still cannot be used until it has been decompressed and decoded. However, other data types are used in the format derived by decryption, with no further processing. For example, related but not limited to television programming, interactive data and metadata (for example program titles) typically require no further processing after decryption. As a result, by “pretending” that video data is not video, it may be possible to fool a system into delivering video in clear compressed format. The video data can then be disseminated rapidly, bypassing all content protection and conditional access schemes.
Throughout the present specification, various encryption algorithms are referred to. Information on the encryption algorithms referred to can be found in Bruce Schneier, Applied Cryptography second edition, 1996, John Wiley and Sons; and in Alfred J. Menezes, Paul C. van Oorschot, and Scott A. Vanstone, A Handbook of Applied Cryptography 1997, CRC Press.
The disclosures of all references mentioned above and throughout the present specification are hereby incorporated herein by reference.